Tell us more about both locations involved:
At home, you have an XP Pro machine, with Remote Desktop enabled, and a user
account with a password, correct?
How does the home location connect to the Internet--what devices are
involved?
At the remote site, you have a Windows or Mac OS/X machine with Remote
Desktop Connection installed. This location connects to the internet how?
You need to know the public IP address of the home network. One way to find
this is to go to
www.myip.com from the home machine.
If there is a nat/router device or firewall involved at home--and there
SHOULD BE! you need to open port 3389, TCP in that firewall or device and
forward inbound traffic on that port to the XP Pro machine.
At the remote site, it is essential that port 3389, TCP traffic be allowed
out--this may not be the case in a network with a firewall connecting to the
Internet.